title: Prospective contralateral eye study to compare 80- and 120-μm flap LASIK using the VisuMax femtosecond laser.
abstract: OBJECTIVE
  To compare visual outcomes and flap stability of LASIK with ultrathin 80- and 120-μm flaps created with a VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) for moderate to high myopia and to evaluate the effect of corneal flap thickness on outcomes.
  
  
  METHODS
  In a prospective contralateral eye study, 36 consecutive patients (72 eyes) underwent bilateral LASIK for myopia ranging from -2.00 to -10.00 diopters using the VisuMax femtosecond laser and MEL-80 excimer laser (Carl Zeiss Meditec). One eye of each patient was randomized to have the 80-μm flap and the other to the 120-μm flap created with 200-kHz VisuMax femtosecond laser. Preoperative and postoperative tests included visual acuity, manifest refraction, contrast sensitivity, and flap thickness measured by anterior segment optical coherence tomography. Main outcomes and complications were checked at postoperative 1 week and 1, 3, and 6 months.
  
  
  RESULTS
  There were no differences in visual outcome, residual refractive error, or contrast sensitivity between groups during follow-up, except for better uncorrected visual acuity at postoperative 1 day in the 120-μm group. Mean standard deviations of measured flap thickness during follow-up ranged from 3.16 to 3.80 μm in both groups. Opaque bubble layer, a unique complication in femtosecond LASIK, was more frequent in the 80-μm group (7 of 36: 19%) than in the 120-μm flap group (3 of 36: 8%) without a statistically significant difference (P = .301) and was related to thicker central cornea and steeper keratometric value, although it did not influence clinical results. Comparison of the intended versus achieved correction showed no significant differences between groups.
  
  
  CONCLUSIONS
  LASIK using the VisuMax femtosecond laser supplied good clinical results and flap reproducibility in both the 80- and 120-μm flap groups. Patients with relatively thin cornea may benefit from 80-μm flap LASIK.
authors.affiliation: Department of Ophthalmology, Samsung Medical Center Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Dong Hui
authors.initials: DH
authors.lastname: Lim
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Keum
authors.forename: Won-Kyung
authors.initials: WK
authors.lastname: Ju
authors.forename: Jeong-Hye
authors.initials: JH
authors.lastname: Lee
authors.forename: Tae-Young
authors.initials: TY
authors.lastname: Chung
authors.forename: Eui-Sang
authors.initials: ES
authors.lastname: Chung
mesh_terms: D000293:Adolescent; D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology; D003319:Corneal Stroma / Q000473:pathology*; D005260:Female; D006801:Humans; D007431:Intraoperative Complications; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011183:Postoperative Complications; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D013524:Surgical Flaps / Q000473:pathology*; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult